JP2545439Y2 - Battery driven welding equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery-operated welding apparatus, and more particularly to a welding apparatus for protecting a switching element for controlling a welding current from thermal damage when the welding current is short-circuited or near a short-circuited current. It relates to the protection circuit of the machine.

[0002]

2. Description of the Related Art A conventional battery welding machine using a battery as a driving source is configured to perform welding with the circuit configuration shown in FIG. 3 and charge the battery.

In FIG. 3, when a switching element 1 such as a transistor is turned on by a PWM control signal sent from a PWM control signal generating circuit 14 in a controller 2, a battery 3, a reactor 4, a shunt resistor 15, a welding output A welding current flows in the circuits of the terminals 5 and 6 and the switching element 1. When the switching element 1 is turned off, the welding current continues to flow in the circuit of the reactor 4, the shunt resistor 15, the welding output terminals 5, 6, and the commutation diode 7 due to the energy stored in the reactor 4, and the welding output terminals 5 and 6 The arc is extinguished at the welded portion connected between the arc.

On the other hand, a commercial AC power supply 8 is supplied to a primary side of a transformer 11 via a no-fuse breaker 9 and a triac 10 of a charge control element, and a voltage generated on the secondary side is rectified by diodes 12 and 13. After that, the battery 3 is charged, and DC power is supplied to the welded portion.

[0005] A welding current flowing through the shunt resistor 15 is detected, and based on the detected welding current, a PWM control signal is generated by the PWM control signal generating circuit 14 so as to be an optimum current, and a desired constant current characteristic is obtained. Is occurring.

[0006]

When welding is performed, the output voltage between the welding output terminals 5 and 6 decreases, and the shunt resistance 15
Reduces the welding current detected. In order to prevent the decrease in the welding current, the PWM control signal generating circuit 14 generates a PWM control signal for extending the ON time of the switching element 1. As a result, the temperature of the switching element 1 rises, so that a large-capacity switching element 1 must be used, or a configuration in which a plurality of switching elements 1 are connected in parallel has to be employed. Alternatively, when a current in a state close to a short circuit flows, the conventional circuit configuration shown in FIG. 3 has a disadvantage that the welding operation is temporarily interrupted and the switching element 1 must be protected from thermal destruction.

An object of the present invention is to solve the above-mentioned drawback, and when the welding voltage of the welded portion falls below a predetermined voltage, the P input to the switching element 1 is reduced.
Provided is a battery-driven welding apparatus in which a WM control signal is converted into an intermittent signal at a certain cycle and is input to the switching element 1 to suppress a rise in the temperature of the switching element 1, thereby preventing thermal destruction of the switching element 1. It is intended to be.

[0008]

In order to achieve the above object, a battery-operated welding apparatus according to the present invention comprises a welding circuit having a switching element for controlling a welding current, a reactor, a commutation diode, and a battery. A battery welding machine having a configuration including a transformer to which a current power supply is connected and charging a battery with a secondary voltage of the transformer, and a controller including a PWM control signal generation circuit to turn on and off the switching element, A welding voltage detection circuit for detecting a voltage between welding output terminals, a comparator for comparing a predetermined voltage with an output voltage of the welding voltage detection circuit, and, when an output of the comparator is generated, the PWM control signal generation circuit PWM to be created
A short-circuit protection circuit for controlling a control signal, wherein the switching element is protected.

[0009]

FIG. 1 is a block diagram showing an embodiment of a battery-driven welding apparatus according to the present invention, and FIG. 2 is a time chart showing an embodiment of a protection circuit.

In FIG. 1, reference numerals 1 to 15 correspond to those in FIG. 3, 16 is a welding voltage detection circuit, 17 is a comparator, 18 is a short circuit protection circuit, 19 is a differential amplifier, 20
Denotes a comparator, 21 denotes a multivibrator circuit, 22 denotes a NAND gate, 23 denotes a diode, 24 denotes a variable resistor, and 25 denotes an amplifier.

In the present invention, the shunt resistor 15 for detecting the welding current is connected between the switching element 1 and the ground, as shown in FIG. And have obtained the welding current. Based on the welding current output from the amplifier 25, a PWM control signal for turning the switching element 1 on and off is generated from the PWM control signal generation circuit 14.

Since the operations of the welding circuit and the charging circuit are the same as those of FIG. 3, the description is omitted. The welding voltage at the welding portion connected between the welding output terminals 5 and 6 is amplified by the differential amplifier 19 and the variable resistance 2
4 is compared with the reference voltage. The variable resistor 24 determines an allowable welding current value that can avoid the thermal destruction of the switching element 1 described above, and usually includes a reference voltage Vo corresponding to a current that sufficiently protects the switching element 1 from thermal destruction. Is set to

When the voltage between the welding output terminals 5 and 6 detected by the welding voltage detecting circuit 16, that is, the welding voltage is higher than the reference voltage Vo set by the variable resistor 24, the short circuit protection circuit 18 does not operate. The switching element 1 is controlled by a PWM control signal generated from the PWM control signal generation circuit 14.

As shown in FIG. 2, when the welding current increases, the welding voltage between the welding output terminals 5 and 6 decreases.
When an abnormality occurs and the welding current is short-circuited or nearly short-circuited, when the output of the welding voltage detection circuit 16, that is, the voltage at the point a becomes lower than the reference voltage Vo of the comparator 20,
The output of the comparator 20, that is, the potential at the point b becomes H level, and opens the gate of the next-stage NAND gate 22. As a result, the pulse generated by the multivibrator circuit 21 passes through the NAND gate 22 in an inverted manner.

When the inverted pulse is at the L level, that is, when the output point c of the NAND gate 22 is at the L level, the PWM control signal generated from the PWM control signal generating circuit 14 is absorbed via the diode 23 and the switching element 1 The supply of the PWM control signal to the switch is cut off. Then, the PWM control signal generated from the PWM control signal generation circuit 14 is supplied to the switching element 1 only during the period T in which the inverted pulse is at the H level, that is, the output point c of the NAND gate 22 is at the H level. That is, the switching element 1
The PWM control signal is applied at the period of the pulse generated by the multivibrator circuit 21 and during the period T.

As described above, while the abnormality occurs and the welding current is in a short-circuit state or a state close to the short-circuit current, the welding output is reduced.
The destruction of the switching element 1 is prevented. When the welding current returns to normal, the voltage at the output point a of the welding voltage detection circuit 16 becomes higher than the reference voltage Vo determined by the variable resistor 24, and the output of the comparator 20 becomes H level.
The gate of the next-stage NAND gate 22 is closed. That is, the short-circuit protection circuit 18 does not operate, and the PWM control signal generated by the PWM control signal generation circuit 14 is applied to the switching element 1 as it is.

When the welding current is substantially short-circuited or short-circuited for a predetermined time, for example, 3 seconds, the output of the NAND gate 22 may be forced to the L level for a predetermined time. In this case, there is provided a counter which receives the output H level of the comparator 17 and outputs a trigger signal when the H level continues for 3 seconds, and sets the output of the NAND gate 22 to the L level for a predetermined time by the trigger signal. Is provided, a circuit configuration for absorbing the PWM control signal from the PWM control signal generation circuit 14 is obtained.

[0018]

As described above, according to the present invention, when an abnormality occurs in the welded portion and a short-circuit or a current near the short-circuit flows, the short-circuit protection circuit is activated and the PWM control signal is applied to the switching element in an intermittent state. As a result, the switching element is prevented from being thermally destroyed due to the short-circuit current, and the protection of the welding machine can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration of an embodiment of a battery-driven welding device according to the present invention.

FIG. 2 is a time chart of an embodiment of the protection circuit.

FIG. 3 is a configuration diagram of a conventional battery welding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching element 2 Controller 3 Battery 4 Reactor 7 Commutation diode 8 Commercial AC power supply 9 No fuse breaker 10 Triac 11 Transformer 14 PWM control signal generation circuit 15 Shunt resistor 16 Welding voltage detection circuit 17 Comparator 18 Short circuit protection circuit 20 Comparator 21 Multivibrator circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Kikuchi No. 3 Hayakawa, Hayakawa, Nitta-cho, Nitta-gun, Gunma Prefecture Inside the Nitta Plant of Sawafuji Electric Co., Ltd. (72) Inventor Tsutomu Hirano 1-chome, Chuo, Wako, Saitama No.4-1 Inside Honda R & D Co., Ltd. (56) References JP-A-57-60772 (JP, A)

Claims (2)

(57) [Scope of request for utility model registration] 1. A transformer having a primary side connected to an AC power supply, a secondary side connected to a welding output terminal via a rectifier and a reactor, a battery charged by an output of the rectifier, and In a battery-driven welding device including a welding output control unit that controls a current supplied to the welding output terminal via a battery and a commutation diode of the reactor, a welding voltage that detects a potential difference between the welding output terminals. A detection circuit; and a short-circuit protection circuit for limiting a drive signal supplied to the welding output control unit so that an output current decreases when a voltage drop detected by the welding voltage detection circuit is detected to be in a short-circuit state. And a battery-operated welding device. 2. A short-circuit protection circuit comprising: a time comparison circuit for comparing a predetermined time with a time of a short-circuit state detected by the welding voltage detection circuit; and when the time comparison circuit generates an output signal. 2. The battery-driven welding apparatus according to claim 1, further comprising: an interrupting circuit for interrupting the drive signal for a predetermined time, wherein the drive signal is interrupted when the short-circuit state continues for a predetermined time.